Reciprocating piston type engines having weights for balancing primary inertial forces

ABSTRACT

A reciprocating piston type internal combustion engine comprising a small gear rotatably mounted between one of crank arms and a connecting rod by means of a pivot provided on said one crank arm in the same phase as a crank-pin and projecting toward the connecting rod, an internal gear having a number of teeth twice that of said small gear and fixedly mounted on the inner wall of a crankcase in meshing engagement with said small gear, a rotating balance weight provided on said small gear in such a way that it is in its lower position when the crank-pin is in the top dead center, and a revolving balance weight provided on the crank arms on the side opposite to the crank-pin with respect to crank journals.

United States Patent Kinoshita 1 Reissued Aug. 12, 1975 1 1RECIPROCATING PISTON TYPE ENGINES [56] References Cited HAVING WEIGHTSFOR BALANCING UNITED S S A N S PRIMARY INERTIAL FORCES 1,163,832 12/1915Lanchester 123/192 B 75 Inventor; Haruo Kinoshita, Hamamatsu 2,271,7662/1942 Huebotter 74/604 Japan 2,807,249 9/1957 Peras 123/192 B 3,626,78612/1971 Kinoshita st 211 74/604 Yamaha Hatsudoki Kabushiki Haisha,Hamakita, Japan [22] Filed: Aug. 1, 1974 [2]] Appl. No.: 493,849

Related US. Patent Documents [73] Assignee:

123/188 C, 197 AC Primary ExaminerSamuel Scott Assistant Examiner-F. D.Shoemaker [5 7 ABSTRACT A reciprocating piston type internal combustionengine comprising a small gear rotatably mounted between one of crankarms and a connecting rod by means of a pivot provided on said one crankarm in the same phase as a crank-pin and projecting toward theconnecting rod, an internal gear having a number of teeth twice that ofsaid small gear and fixedly mounted on the inner wall of a crankcase inmeshing engagement with said small gear, a rotating balance weightprovided on said small gear in such a way that it is in its lowerposition when the crank-pin is in the 1 top dead center, and a revolvingbalance weight provided on the crank arms on the side opposite to thecrank-pin with respect to crank journals.

7 Claims, 6 Drawing Figures Reissued Aug 12, 1975 28512 4 Sheets-Sheet lINVENTOR HARU KI/YOSHITA ATTOR EY Reissued Aug. 12, 1975 7 Re. 28,512

4 Sheets-Sheet 2 INVENTOR HA RGO KINOSHITA' Reissued Aug. 12, 1975 Re.28,512

4 Sheets-Sheet s @"k; Cl cz INVENTOR HA Ruo mlvo SHITA ATTO EY ReissuedAug. 12, 1975 Re. 28,512

4 Sheets-Sheet 4 lNVENTOR HARUO K/NOS/HTA BY g I ATTORN Y RECIPROCATINGPISTON TYPE ENGINES HAVING WEIGHTS FOR BALANCING PRIMARY INERTIAI,FORCES Matter enclosed in heavy brackets I: appears in the originalpatent but forms no part of this reissue specification; matter printedin italics indicates the additions made by reissue.

BACKGROUND OF THE INVENTION I. Field of the Invention This inventionrelates to a reciprocating piston type internal combustion engine havinga piston-crank mechanism in which primary inertia force can be perfectlybalanced.

2. Description of the Prior Art The applicant has already proposed inPatent Application Ser. No. 5,875, new U.S. Pat. No. 3,626,786, apiston-crank mechanism or a reciprocating piston type internalcombustion engine in which a revolving bal ance weight is provided onthe side opposite to a crankpin of a crank arm fixed on a crank-journaland supporting the crank-pin, while a small gear having a rotatingbalance weight is coaxially mounted on the crankpin, and said small gearis held in meshing engagement with an internal gear fixedly mounted in acrankcase and having a number of teeth twice that of said small gear andis connected to a piston by a connecting rod. whereby the forces ofinertia caused by the reciprocating motion of the piston aresubstantially completely balanced to minimize vibrations. However, thistype of piston-crank mechanis. because of a large number of componentparts. becomes complicated in construction and large in size, and canhardly be put in practical use.

SUMMARY OF THE INVENTION A primary object of the present invention is toimprove the reciprocating piston type internal combustion engine of thetype described above.

Another object of the invention is to obtain a highly practicalconstruction of the reciprocating piston type internal combustion enginewhich is comprised of a minimum number of component parts and simple andcan be easily produced with high productivity and at a lost cost.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a vertical sectional viewshowing one embodiment of the present invention;

FIG. 2 is a transverse sectional view taken along the line IIII of FIG.1;

FIGS. 3 and 4 are diagraminatical views for explaining the operation ofthe embodiment shown in FIGS. I and 2;

FIG. 5 is a vertical sectional view showing another embodiment of theinvention; and

FIG. 6 is a diagrammatical view for explaining the operation of theembodiment shown in FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the inventionwill be described with reference to FIGS. 1 to 4. Referring first toFIG. 1, reference numeral I designates a crankcase, 2 a cylinder. 3 acylinder head, 4 a piston which makes a reciprocating motion within thecylinder 2, S a connecting rod connected with the piston 4 and 6 crankjournals. Crank arms 7 are formed on the crank journals 6 extending atright angles thereto and a crank-pin 8 is fixed to the crank arms 7 withthe opposite ends thereof being force-fitted into said crank arms 7. Thecrank journals 6, crank arms 7 and crankpin 8 constitute a crank-shaft.The crank-pin 8 rotatably supports the large diameter end 9 of theconnecting rod 5.

In the present invention, an internal gear 10 is fixedly mounted in thecrankcase l and a small gear 11 having a number of teeth one-half ofthat of said internal gear I0 and meshing with said internal gear 10 isrotatably mounted on the crank-pin 8 in side-by-side relation with thelarge diameter end 9 of the connecting rod 5. Reference numeral 12designates a needle bearing interposed between the large diameter end 9of the connecting rod 4 and the crank-pin 8, and 12a designates anotherneedle bearing interposed between the small gear 11 and the crank-pin 8.The small gear II is formed with a rotating balance weight 13 on itsside face facing the large diameter end 9 of the connecting rod 5 insuch a way that said rotating balance weight will be in its downwardposition when the crank-pin 8 is in its upward position. while the crankarms 7 are formed with revolving balance weights 14 in opposite phaserelation with the crank-pin 8. Reference numeral 15 designates ballbearing supporting the crank journals 6, 16 oil seals and 17 thrustwashers.

In the reciprocating piston type internal combustion engine constructedas described above. when the piston 4 makes a reciprocating motion, thesmall gear I] in meshing engagement with the internal gear 10 fixedlymounted on theinner wall of the crankcase I bodily revolves round thecenter line the crank journals 6 while rotating round its own axis.Since the large diameter end 9 of the connecting rod 5 is rotatablymounted on the crank-pin 8 coaxially with the small gear II, the centerof the crank-pin 8 moves incident to the reciprocating motion of thepiston 4 along a circle having a radius l which is the length of thecrank arms 7 (refer to FIG. 3).

Of all the masses connected to the crank-pin 8, with mA representing thereciprocating mass at the piston (the sum of the masses of the piston 4and its accessories the reciprocating mass of the connecting rod 5, andthe mass of a bearing at the small diameter end of the connecting rod).and mD representing the rotating mass (the sum of the rotating mass ofthe connecting rod and the mass of the hearing at the large diameter endof the connecting rod 5 mB representing the mass of the rotating balanceweight 13 on the small gear 11 which is a rotating portion, and mCrepresenting the mass of the revolving balance weights 14 on the crankarms 7 which are revolving portions, the primary forces of inertia ofthe largest absolute values F F F F F F F and P of all the lateral andvertical forces of inertia of these masses mA, mB, mC and mD arerespectively represented by the following formulae. using the rotationalangle 6 of the crank arms as parameter:

FAY 0 F mD-l ((dH/dtF sin 6 d'-6/dt cos 6 wherein R the distance betweenthe center of gravity of the rotating balance weight m8 and the centerline of the crank-pin 8 R the distance between the center of gravity ofthe revolving balance weight rnC and the center line of the crankjournals 6 Here, when the arrangement is made to satisfy the conditionalequations mB- R 1/2 mA rnC- R mB l/2 mA mDl the following results willbe obtained:

ax ax ax l nx= FAY+ F 'l" DCY+ FDYZO Namely, in the construction shownin FIGS. 1 and 2 the primary forces of inertia can be completelybalanced, provided that the above conditions are satisfied.

In the above embodiment. as may be apparent from FIGS. I and 4. thereciprocating mass mA and the rotating balance weight mass mB do notmove in one plane. Therefore, a periodically varying unbalanced momentwhich makes the engine to rotate about a vertical axis and a horizontalaxis perpendicular to the crank shaft will result. This unbalancedmoment when represented by vector, varies according to the angularposition of the crank-shaft in respect of its absolute value and phase.However, the maximum absolute value of this unbalanced moment becomessmall when a plane of application C of the resultant force of thecentrifugal forces created by the revolving balance weights mt: and mC-is located between the center line A of the piston 4 or an axis A alongwhich the center of gravity of the reciprocating mass mA reciprocatesand a plane of application B of the rotating balance weight mB as shownin FIG. 4, and becomes smallest especially when the following conditionis satisfied:

where e the distance between the line or axis A and the plane ofapplication C b the distance between the line or axis A and the plane ofapplication B l the distance between the center line of the crankpin 8and the center line of the crank journals 6 R the distance between thecenter of gravity of the rotating balance weight mB and the center lineof the crank-pin 8 According to the present invention, as describedabove, the primary forces of inertia can be completely balanced andvibrations can be decreased to a practically acceptable degree. Further,since only one small gear 1 I is mounted on the crank-pin 8 and therotating balance weight 13 is provided only on the small gear 11, thenumber ofcomponent parts can be reduced to a minimum and theconstruction can be simplified. Furthermore, since the amount ofeccentricity of the rotat ing balance weight I3 can be decreased byproviding said rotating balance weight 13 on the side face of the smallgear ll facing the large diameter end 9 of the connecting rod, theunbalanced moment resulting from misalignment of the center of theengine and the center of gravity of the rotating balance weight l3 canbe reduced in amount to a substantially negligible degree. and can befurther reduced by shifting the revolving balance weight mC toward therotating balance weight mB as stated above.

Still further, since the large diameter portion 9 of the connecting rod5 and the small gear I I are mounted on the crank-pin 8 in adjacentside-byside relation so that they are rotatable independently of eachother relative to said crank-pin, a torque is transmitted from the largediameter end 9 to the crank-shaft directly through the crank-pin 8 anddoes not act on the small gear 11. Therefore. the material of the smallgear I] is not required to be of high strength. For instance, the smallgear 1 l and the rotating balance weight 13 can be integrally moldedofsintered alloys and the internal gear 10 can be molded of syntheticresins. Thus, these parts can be easily produced with high productivityand cooperate without generating noises.

The large diameter end 9 of the connecting rod 5 and the small gear 11are rotatably mounted on the crankpin 8 independently of each other, sothat they can be readily mounted and demounted individually, renderingthe assembly and disassembly of the mechanism easy. The small gear 11rotates relative to the crankshaft at a rate of speed twice as high asthat of the latter, and hence the erank-pin 8 and the needle bearing 12atherefor undergo severe conditions. However, the needle bearing 12a canbe lubricated in a manner similar to the large diameter end 9 of theconnecting rod easily, without requiring any special lubricating system.

In FIGS. 5 and 6 there is shown another embodiment of the invention.This embodiment is the same as the preceding embodiment, with only theexception that a crank-pin 81 has a different shape from that in thepreceding embodiment. In FIGS. 5 and 6. same parts as those in thepreceding embodiment are indicated by same numerals and the descriptionsthereof are omit tedv The crank-pin 81 is not straight but cranked toprovide an outer pivot 82 and an inner pivot 83 which are a distance reccentric relative to each other. The outer pivot 82 is force-fittedinto the right hand crank arm 7 and has the large diameter end 9 of theconnecting rod rotatably mounted thereon. The inner pivot 83 isforcefitted into the left hand crank arm 7 in the same phase as theouter pivot 82 with respect to the crank-shaft but offset toward thecrank journals 6 or inwardly relative to the outer pivot 82, and has thesmall gear 11 rotatably mounted thereon. A flange 84 is formed betweenthe outer pivot 82 and the inner pivot 83 of the crankpin 8] to hold thelarge diameter end 9 of the connecting rod 5 and the small gear IIagainst lateral movement as well as to prevent a strength reduction ofthe crank-pin 81.

In this embodiment constructed described above, when the piston 4 makesa reciprocating motion, the center of the large diameter end 9 of theconnecting rod 5 or the center of the outer pivot 82 move along a circleof a radius 1, i.e., the length of the crank arms 7, incident to thereciprocating motion (refer to FIG. 6). The small gear I] rotates roundits own axis in meshing engagement with the internal gear 10 whileconcurrently bodily revolving round the crank journal 6 together withthe inner pivot 83.

It will be understood that in this embodiment also, similar to thepreceding embodiment. the primary forces of inertia are completelybalanced provided that the following conditions are satisfied: mB-Rl/Z'mA mC-R mB( l r) 1/2 mA mDl The unbalanced moment which tends tocause the engine to rotate about a vertical axis and a horizontal axisperpendicular to the crank-shaft can be decreased in the similar manneras in the preceding embodiment.

In this embodiment, as stated above, the axis of the inner pivot 83having the small gear ll rotatably mounted thereon is offset toward thecrank journal 6 relative to the outer pivot 82 having the large diameterend 9 of the connecting rod rotatably mounted thereon. Therefore. thediameter of the internal gear 10 can be made small relative to thepiston stroke and the internal setup of the crankcase can be madecompact. Consequently, the entire engine can be compact and small insize. Particularly in case of a crank chamber compression type two cycleengine, the internal space of the crankcase can be decreased, thepreliminary compression efficiency can be enhanced and the engine outputcan be increased.

Furthermore, with reference to the revolving balance weight 14 providedon the crank arms 7 on the side opposite to the crank-pin 8, the weightthereof can be reduced since the small gear ll having the rotatingbalance weight 13 is positioned relatively close to the axis of thecrank-shaft.

Although the present invention has been described and illustrated hereinin terms of specific embodiments thereof, it should be understood thatthe invention is not restricted to the details of the embodiments shownbut many changes and modifications are possible within the scope of theappended claims.

I claim:

1. A reciprocating piston type internal combustion engine having acrankcase, a crank-shaft rotatably mounted in said crankcase andincluding crank journals, crank arms and a crank-pin, a piston and aconnecting rod having the opposite ends thereof rotatably connectedtosaid crank-pin and said piston respectively, said engine'comprising a.a pivot provided on one of the crank arms in the that of said small gearand fixed to the crankcase in meshing engagement with said small gear,

(1. a rotating balance weight provided on said small gear adjacent toone side of the connecting rod in such a way that it will be in itslower position when the crank-pin is in the top dead center. and

e. revolving balance weight provided on said crank arms on the sideopposite to the crank-pin with respect to the crank journals;

2. A reciprocating piston type internal combustion engine according toclaim 1, wherein said crank-pin and said pivot are an integral straightpin.

3. A reciprocating piston type internal combustion engine according toclaim l,-wherein said crank-pin and said pivot respectively consist ofan [inner] outer pivot and an [outer] inner pivot which are connectedintegrally with each other in the shape of a crank, and

the inner pivot has the small gear rotatably mounted thereon, while theouter pivot has the large diameter end of the connecting rod rotatablymounted thereon,

and further the inner pivot is located closer to the crank journals thanthe outer pivot.

4. A reciprocating piston type internal combustion engine according toclaim 2, wherein wherein mA the reciprocating mass added to thepiston-pin mB the mass of the rotating balance weight mC the mass of therevolving balance weight mD the rotating mass added to the crank pin 1the distance between the center line of the crankpin and the center lineof the crank journals R the distance between the center of gravity of VmB and the center line of the crank-pin R 1 the distance between thecenter of gravity of mC and the center line of the crank journals. 5. Areciprocating piston type internal combustion engine according to claim3, wherein 6. A reciprocating piston type internal combustion engineaccording to claim 4, wherein wherein C the distance between an axisalong which the center of gravity of the reciprocating mass reciprocatesand a plane of application of the resultant force of the centrifugalforces created by the revolving balance weight I b the distance betweenan axis along which the center of gravity of the reciprocating massreciprocates and a plane'of application of the resultant force of thecentrifugal forces created by the rotating balance weight l the distancebetween the center line of the crankpin and the center line of the crankjournals R the distance between the center of gravity of the rotatingbalance weight and the center line of the crank-pin 7. A reciprocatingpiston type internal combustion engine having a crankcase, o crank-shaftrotatably mountcd in said crankcase and including,' crank journals,crank arms and a crank-pin, a piston and a connecting rod having theopposite ends thereof rotatably connected to said crank-pin and saidpiston respectively, said engine comprising at. a pivot provided on oneof thc crank arms in the same phase as and rigidly/ital to the crank-pinand protruding toward the connecting rod,

1). a small gear rotatably mounted on said pivot and hflllg in .Si(l(-l7\-Sl(lt relation with the large diameter and oft/1c connecting rod,

c. on internal gcor having a number oflceth twice that ofsaid small gearundjixcd to the crankcase in meshing engagement with said .S'Hltlllgcur,

d. a rotating balance weight provided on said small gear in such a waylhul it will be in its lower position when the crunkpin is in the topdead center, and

c. revolving lmluncc weight provided on said crank arms on the sideopposite to the crank-pin with rcspect to the crunkjournuls.

1. A reciprocating piston type internal combustion engine having acrankcase, a crank-shaft rotatably mounted in said crankcase andincluding crank journals, crank arms and a crank-pin, a piston and aconnecting rod having the opposite ends thereof rotatably connected tosaid crank-pin and said piston respectively, said engine comprising a. apivot provided on one of the crank arms in the same phase as and rigidlyfixed to the crank-pin and protruding toward the connecting rod, b. asmall gear rotatably mounted on said pivot between said one of the crankarms and the connecting rod, and being in side-byside relation with thelarge diameter end of the connecting rod, c. an internal gear having anumber of teeth twice that of said small gear and fixed to the crankcasein meshing engagement with said small gear, d. a rotating balance weightprovided on said small gear adjacent to one side of the connecting rodin such a way that it will be in its lower position when the crank-pinis in the top dead center, and e. revolving balance weight provided onsaid crank arms on the side opposite to the crank-pin with respect tothe crank journals.
 2. A reciprocating piston type internal combustionengine according to claim 1, wherein said crank-pin and said pivot arean integral straight pin.
 3. A reciprocating piston type internalcombustion engine according to claim 1, wherein said crank-pin and saidpivot respectively consist of an (inner) outer pivot and an (outer)inner pivot which are connected integrally with each other in the shapeof a crank, and the inner pivot has the small gear rotatably mountedthereon, while the outer pivot has the large diameter end of theconnecting rod rotatably mounted thereon, and further the inner pivot islocated closer to the crank journals than the outer pivot.
 4. Areciprocating piston type internal combustion engine according to claim2, wherein mB.RB l/2.mA mC.Rc mB.l + l/2.mA + mD.l wherein mA : thereciprocating mass added to the piston-pin mB : the mass of the rotatingbalance weight mC : the mass of the revolving balance weight mD : therotating mass added to the crank pin l : the distance between the centerline of the crank-pin and the center line of the crank journals RB : thedistance between the center of gravity of mB and the center line of thecrank-pin RC : the distance between the center of gravity of mC and thecenter line of the crank journals.
 5. A reciprocating piston typeinternal combustion engine according to claim 3, wherein mB.RB l/2.mAmC.RC mB.(l-r) + l/2.mA + mD. wherein mA, mB, mC, mD, l, RB and RC havethe meanings as defined in claim 4 and r is the distance between thecenter line of the inner pivot and the center line of the outer pivot.6. A reciprocating piston type internal combustion engine according toclaim 4, wherein C l/l + RB.b wherein C : the distance between an axisalong which the center of gravity of the reciprocating mass reciprocatesand a plane of application of the resultant force of the centrifugalforces created by the revolving balance weight b : the distance betweenan axis along which the center of gravity of the reciprocating massreciprocates and a plane of application of the resulTant force of thecentrifugal forces created by the rotating balance weight l : thedistance between the center line of the crank-pin and the center line ofthe crank journals RB : the distance between the center of gravity ofthe rotating balance weight and the center line of the crank-pin.
 7. Areciprocating piston type internal combustion engine having a crankcase,a crank-shaft rotatably mounted in said crankcase and including crankjournals, crank arms and a crank-pin, a piston and a connecting rodhaving the opposite ends thereof rotatably connected to said crank-pinand said piston respectively, said engine comprising a. a pivot providedon one of the crank arms in the same phase as and rigidly fixed to thecrank-pin and protruding toward the connecting rod, b. a small gearrotatably mounted on said pivot and being in side-by-side relation withthe large diameter end of the connecting rod, c. an internal gear havinga number of teeth twice that of said small gear and fixed to thecrankcase in meshing engagement with said small gear, d. a rotatingbalance weight provided on said small gear in such a way that it will bein its lower position when the crank-pin is in the top dead center, ande. revolving balance weight provided on said crank arms on the sideopposite to the crank-pin with respect to the crank journals.